The present invention relates to thermoelectric coolers (TEC's).
It is known to use a thermoelectric cooler to lower the operating temperature of a semiconductor device such as a laser. A thermoelectric cooler includes a plurality of thermoelectric cooling elements, which are constructed of materials with dissimilar characteristics. The elements are connected electrically in series and thermally in parallel to provide a plurality of thermoelectric couples. Each thermoelectric couple includes one element having a first characteristic and another element having a second characteristic. The thermoelectric couples are connected between two plates which function as a hot side and a cold side of a thermoelectric cooler. The hot side is thermally connected to a heat sink and the cold side is thermally connected to the semiconductor device.
Thermoelectric cooling is achieved by passing a DC electric current through the thermoelectric cooler. Thermal energy is drawn from the cold side to the hot side at a rate which is proportional to current passing through the circuit and the number of couples. At the hot side, the thermal energy is dissipated by the heat sink. The thermoelectric cooling effect is greatly increased when the dissimilar conducting materials used are semiconducting materials.
The dissimilar semiconducting materials generally used for thermoelectric cooling are N-type material (more electrons than necessary to complete a perfect molecular lattice structure) and P-type material (fewer electrons than necessary to complete a perfect molecular lattice structure, thus providing holes). The extra electrons in the N-type material and the holes in the P-type material are called "carriers" which function to move the thermal energy from the cold side to the hot side.